Astrocyte dysfunction in epileptogenesis: the role of adenosine Project Summary/Abstract This grant proposal studies the hypothesis that astrogliosis and resulting dysfunction of adenosine-based neuromodulation is a mechanistic cause for the development of epilepsy (i.e. epileptogenesis). This is of importance, since to date no effective prophylaxis for epilepsy is available. This proposal will explore status epilepticus (SE)- triggered epileptogenesis and dysfunction of the endogenous adenosine-based seizure control system in mice in search for an astrocyte-based mechanism of epileptogenesis and thus may provide a foundation for the development of novel antiepileptogenic therapies. The proposal is based on the following findings: (i) Adenosine kinase (ADK) is the key enzyme for the regulation of adenosine; (ii) In adult brain, ADK is expressed in astrocytes; (iii) Astrogliosis is a hallmark of epileptogenesis; (iv) ADK is over-expressed within epileptic astrogliotic hippocampus; (v) Augmentation of adenosine by implants of adenosine releasing cells prevents kindled seizures. (vi) Transgenic overexpression of ADK increases seizure susceptibility; (vii) Local reduction of ADK in transgenic mice prevents epileptogenesis. Our CENTRAL HYPOTHESIS is that an epileptogenesis triggering event (e.g. SE) induces astrogliosis with resultant regional upregulation of ADK as a necessary component of epileptogenesis and that reconstitution of brain adenosine by stem cell derived brain implants can prevent such epileptogenesis. The model system to address this hypothesis consists of intraamygdaloid application of kainic acid (KA) to initiate epileptogenesis selectively in the CA3 area of the hippocampal formation of mice and to transplant ADK-deficient adenosine releasing embryonic stem (ES) cells into the epileptogenic region. SPECIFIC AIMS: In Aim 1 we will study the causal, temporal, and spatial relations of astrogliosis, upregulation of ADK and seizures in a mouse model of CA3-selective epileptogenesis. In Aim 2 we will use a panel of different Adk-transgenic mice, in which we can molecularly separate cell-type specific functions of ADK expression from astrogliosis, to study both mechanisms independently. In Aim 3 we will use ADK-deficient ES cell-derived intrahippocampal implants in a therapeutic approach to prevent epileptogenesis. The expected outcome of these studies is to define astrocytic ADK as a target for the prevention of epileptic seizures and to translate these findings into a novel stem cell based treatment approach.